Optional high voltage booster circuit for indicator tube

ABSTRACT

The disclosure is of a circuit for driving an indicator tube of the type including an anode and a plurality of glow cathode electrodes. The circuit includes a normal anode power supply and an auxiliary circuit for increasing the voltage supplied to the anode of the tube by a fractional amount of the voltage supplied by the normal power supply during periods when the normal power supply is insufficient to fire the tube.

United States Patent [72] Inventor Arthur F- Cake 2,954,507 9/1960 Kitzet al 315/846 X Orange, NJ- 3,321,666 5/1967 Gamett et a1. 315/224 X[21] Appl. No. 742,032 3,365,611 1/1968 Yii 315/84.6 [22] Filed July 2,1963 3,486,067 12/1969 Griffith et al 315/846 [45] Patented Aug. 17,1971 OTHER REFERENCES [73] Asslgnee 32 Cwpmm" Hoffman, IBM Tech. Discl.BulL, Vol. 7, No. 2, Page 127 trolt, Mich.

(July 1964) Bruce et aL, IBM Tech. Discl. Bull., Vol. 8, No. 4, pp.649-- 541 OPTIONAL HIGH VOLTAGE noosrmz CIRCUIT 1- 1965) FOR INDICATORTU Primary Examiner-John W. Huckert 2 Claims, 1 Drawing Fig. AssistantExaminer-William Larkins 52] us. Cl 315/169 R, ff'f Kemeh Miller andGreen 315/169 T,315/224,315/233,315/245,315/260, rwmn W i v l 315/287,315/337 3-. re e W New. V .W. i [51] Int. Cl ..H0lj 61/66, V

H02m 7/52 ABSTRACT: The disclosure is of a circuit for driving an in-[50] Field of Search 315/101, dicatmtube f the typa including an anodeand a plurality f I69, 260, i i i i r glow cathode electrodes. Thecircuit includes a normal anode 2 84-6;3Q7/263i109, 110 power supply andan auxiliary circuit for increasing the volt age supplied to the anodeof the tube by a fractional amount of [56] Rderences Cited the voltagesupplied by the normal power supply during UNITED STATES PATENTS periodswhen the normal power supply is insufficient to fire 2,769,939 11/1956Williams 7. 315/240 X Ll i e tll b i V w 12 V2.0 10 C I RB '30 I 16 s454 SWITCH] SWlTCH SWITCH PATENTED AUG] 54 swncul INVENTUR. ARTHUR F.CAKE ATTORNEY OPTIONAL IIIGI-I VOLTAGE BOOSTER CIRCUIT FOR INDICATORTUBE BACKGROUND OF TI IE INVENTION example, when a tube is operated. ata higher-than-normal temperature.

SUMMARY OF THE INVENTION Inorder to overcome the foregoing problem, ananode driving circuit utilizes a capacitor that is charged to apredetermined level determined by a pair of resistors acting as avoltage divider. This capacitor is thereafter automatically connected tothe anode power supply so the voltage on the capacitor is aiding thepower supply voltage when the tube is nonconducting. A boosted supplyvoltage that is just sufficient to tire the tube when hot, yet not sogreat as to stress it, is applied to the tube by choosing the requisiterelative values of the two resistors forming the voltage divider.

DESCRIPTION OF THE DRAWING In the drawing, the single FIGURE is aschematic representation of a circuit embodying the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The circuit of the invention isparticularly adapted for use with cathode glow indicator tubes of thetype known as Pat. Nix-tubes. This type of tube 10 is shownschematically in the drawing and includes a gas-filled envelope whichcontains an anode electrode 20 and usually ten cathode electrodes'30including the numerals to 9." Each-cathode electrode'is coupled to aswitch or driver circuit 34 which is used to select the cathode to bedisplayed; These driver circuits are well known in the art and maycomprise switching transistors that are turned on or off as required tofire the appropriate cathode. One type of driver circuit for thispurpose is described in patent 3,227,922.

According to the invention, the anode electrode 20 is connected to theanode of diode 40, which has its cathode connected to the source 50 of afield effect transistor 60. The drain 70 of the transistor 60 isconnected to a positive DC power source V which, in a typical circuit,is of the order of 200 volts. A resistor 80 is connected between thedrain 70 and the source 50, and the gate 90 of the transistor 60 isconnected both through a resistor 100 to the junction of its source andthe anode of diode 40 and to the collector of an NPN transistor 110which has its emitter connected to ground and its base connected througha suitable input impedance 120 to any well-known source of positivepulses 130. A capacitor 140 is connected between the collector of thetransistor 110 and the cathode of diode 40.

The circuit shown is one which is used to overcomethe problem describedabove, and it can also be used for dimming or blanking the tube bycontrolling the frequency of pulses 130 so that the duty cycle of thecurrent -flow through the tube is decreased. Circuitry to control pulses130 is well known in the art and is not seen as requiring explanationhere. In operation, the circuit responds to pulses 130 in the followingmanner. As the positive pulses 130 are fed into the base of thetransistor 110, each pulse turns on the transistor 110, and this the tube, its glowappears to be continuous and the periodic blanking is notVlSlb e. If the repetition rate of pulses 130 is increased significantlyso that the tube is blanked more frequently, then a glowing cathode canbe dimmed.

The circuit solves the problem described above where the tube 10 doesnot operate with the normal voltage applied to it as follows.

Each input pulse 130 turns on transistor 1 10, sets its collector atabout ground and thus turns off transistor 60. Resistors and comprise avoltage divider. When transistor 10 turns on and its collector isgrounded, point A, which is the intersection of the cathode of diode 40,the source 50 of field effect transistor 60 and the junction ofresistors 80 and 100, will have a potential determined by the resistancevalues of resistors 80 and 100. Assuming this potential to be about 100volts, capacitor 140 charges to about 100 volts through diode 40. Thus,there is +100 volts at point A and at point B, the intersection of oneside of capacitor 140, anode 20 and the anode of diode 40. Thispotential may be insufiicient, however, to fire tube 10. When thetransistor turns off, point C, which is the intersection of gate 90 offield effect transistor 60, the other side of capacitor and thecollector of transistor 110, and point A rise toward 200 volts, and,therefore, the gate of transistor 60 approaches turn-on potential. Whentransistor 60 turns on, it becomes a low impedance path so that point Cis now connected to about +200 volts through resistor 100 and point A.If tube 10 is nonconducting, point C effectively has a potential of +200volts that is summed with the +100 volts across the capacitor 140 sothat a maximum of about +300 volts is placed at point B and at the anode20 of the indicator tube, thus causing the indicator tube to fire.

l claim:

l. A circuit for firing a gas discharge device having at least one pairof electrodes comprising:

a first current path including a first electronic switch connected toone electrode of said pair of electrodes through a unidirectional devicefor connecting a positive potential source to said one electrode;

a second current path including a second electrode switch connected tosaid one electrode through a capacitor for connecting a ground potentialsource to said one electrode;

a first resistor shunting said first switch in said first current path;

a second resistor connected between the first electronic switch and theunidirectional device in said first current path and between thecapacitor and second electronic switch in said second current path; and

means interacting with said second resistor for causing the firstelectronic switch to close when said second electronic switch is openedand open when said second electronic switch is closed, whereby saidcapacitor is charged to a fraction of the potential of said potentialsource when said first electronic switch is open and said second switchis closed and is connected to the positive potential source in a seriesaiding relationship when said second switch is open and said firstswitch is closed and said discharge device is nonconducting.

2. The circuit of claim I wherein said first and second electronicswitches comprise first and second transistors and wherein said meanscomprises a current path from said second current path between thecapacitor and second switch to the gate of said first transistor.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,600,631 Dated August 17 197l Inventor) Arthur F. Cake It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

The title should be --VOLTAGE BOOSTER CIRCUI'I FOR INDICATOR TUBE--.Column 1, lines 37 & 38 delete "Pat. No." and substitute therefor--NIXIE--. Column 2, line 44 change "electrode" to --electronic-; andline 65 after "transistors" insert -the first transistor having a drain,source and gate, and the second transistor having a collector, a baseand an emitter,--.

Signed and sealed this 21st day of March 1972.

(SEAL) Attest 3 EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK AttestingOfficer Commissioner of Patents 1 M Po 0 69} USCOMM-DC wave-poo U 5.GOVEFHNENT FRINT'NG OFFICE I 1'. O-355-JJ4

1. A circuit for firing a gas discharge device having at least one pairof electrodes comprising: a first current path including a firstelectronic switch connected to one electrode of said pair of electrodesthrough a unidirectional device for connecting a positive potentialsource to said one electrode; a second current path including a secondelectrode switch connected to said one electrode through a capacitor forconnecting a ground potential source to said one electrode; a firstresistor shunting said first switch in said first current path; a secondresistor connected between the first electronic switch and theunidirectional device in said first current path and between thecapacitor and second electronic switch in said second current path; andmeans interacting with said second resistor for causing the firstelectronic switch to close when said second electronic switch is openedand open when said second electronic switch is closed, whereby saidcapacitor is charged to a fraction of the potential of said potentialsource when said first electronic switch is open and said second switchis closed and is connected to the positive potential source in a seriesaiding relationship when said second switch is open and said firstswitch is closed and said discharge device is nonconducting.
 2. Thecircuit of claim 1 wherein said first and second electronic switchescomprise first and second transistors and wherein said means comprises acurrent path from said second current path between the capacitor andsecond switch to the gate of said first transistor.